As a material for automobiles, particularly an insulating covering material for protecting electric wires, polyvinyl chloride resin has hitherto been used. Since polyvinyl chloride is a self-extinguishing material, it has a high flame-retardancy and also is a material excellent in flexibility and abrasion resistance. However, there is a problem that the polyvinyl chloride may generate harmful halogen gasses at vehicle fire or incineration thereof and hence non-halogen-based protective materials have been developed.
In halogen-free frame-retardant resin compositions, a metal hydrate such as magnesium hydroxide or aluminum hydroxide is employed as a frame retardant. In Patent Document 1, 200 to 300 parts by mass of a metal hydrate and 5 to 60 parts by mass of zinc borate are blended into 100 parts by mass of ethylene-vinyl acetate copolymer.